JP6955745B2 - Polyamide resin composition and foam molded product made of the same - Google Patents

Description

The present invention relates to a polyamide resin composition and a foam molded product made of the same.

Aliphatic general-purpose polyamide resins typified by polyamide 6 and polyamide 66 have excellent properties such as chemical resistance, rigidity, slidability, and moldability, and are therefore used in a wide range of applications. The foam molded product is being studied for application to cushioning materials, packaging materials, building materials, etc. by taking advantage of its light weight, cushioning property, heat resistance, and the like.

Since the polyamide resin is a resin having a low melt viscosity and elongation viscosity, the foamed molded product of the polyamide resin has conventionally been added with a cross-linking agent or a foaming agent to thicken the polyamide resin in a single-screw extruder. Is produced by melting and extruding foam (chemical foaming method), or by extruding foaming with a gas expanded by a temperature change or pressure change (physical foaming method). However, the foam molded product of the polyamide resin alone does not have sufficient mechanical strength such as impact strength. Therefore, the present inventors have proposed in Patent Document 1 a polyamide resin composition for core back injection foam molding containing finely divided cellulose fibers.

International Publication 2014/171430 Pamphlet

However, although the polyamide resin composition of Patent Document 1 was a resin composition suitable for the core back method, it was not possible to produce a foam molded product by extrusion foam molding because of its low elongation viscosity.

The present invention solves the above-mentioned problems, and an object of the present invention is to provide a polyamide resin composition suitable for extrusion foam molding.

The present inventors have arrived at the present invention as a result of repeated diligent studies to solve the above problems.
That is, the gist of the present invention is as follows.
(1) Polyamide containing 100 parts by mass of a polyamide resin, 0.1 to 10.0 parts by mass of cellulose fibers having an average fiber diameter of 10 μm or less, and 0.1 to 5.0 parts by mass of trimethylolpropane polyglycidyl ether. Resin composition .
(2) (1) Symbol placement foamed molded article comprising the polyamide resin composition.

According to the present invention, it is possible to provide a polyamide resin composition suitable for extrusion foam molding. The foam molded product made of the polyamide resin composition of the present invention can be used for various purposes such as cushioning materials, packaging materials, and building materials.

The polyamide resin composition of the present invention contains a polyamide resin, cellulose fibers having an average fiber diameter of 10 μm or less, and a foam nucleating agent.

The polyamide resin used in the present invention refers to a polymer having an amide bond formed from an aminocarboxylic acid, lactam or diamine and a dicarboxylic acid.

Examples of aminocarboxylic acids include 6-aminocaproic acid, 11-aminoundecanoic acid, 12-aminododecanoic acid, and 4- (aminomethyl) benzoic acid.

Examples of the lactam include ε-caprolactam and ω-laurolactam.

Examples of the diamine include tetramethylenediamine, hexamethylenediamine, nonamethylenediamine, decamethylenediamine, undecamethylenediamine, dodecamethylenediamine, 2,2,4- / 2,4,4-trimethylhexamethylenediamine, and 5 -Methyl nona methylene diamine, 2,4-dimethyl octamethylene diamine, metaxylylene diamine, paraxylylene diamine, 1,3-bis (aminomethyl) cyclohexane, 1-amino-3-aminomethyl-3,5,5 -Trimethylcyclohexane, 3,8-bis (aminomethyl) tricyclodecane, bis (4-aminocyclohexyl) methane, bis (3-methyl-4-aminocyclohexyl) methane, 2,2-bis (4-aminocyclohexyl) Examples include propane and bis (aminopropyl) piperazine.

Examples of the dicarboxylic acid include adipic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, 2-chloroterephthalic acid, 2-methylterephthalic acid and 5-methylisophthalic acid. , 5-Sodium sulfoisophthalic acid, hexahydroterephthalic acid, hexahydroisophthalic acid, diglycolic acid and the like.

Specific examples of the polyamide resin used in the present invention include polycaproamide (polyamide 6), polytetramethylene adipamide (polyamide 46), polyhexamethylene adipamide (polyamide 66), and polyhexamethylene sebacamide (polyamide 66). 610), polyhexamethylene dodecamide (polyamide 612), polyundecamethylene adipamide (polyamide 116), polyundecaneamide (polyamide 11), polydodecaneamide (polyamide 12), polytrimethylhexamethylene terephthalamide (polyamide TMHT) ), Polyhexamethylene terephthalamide (polyamide 6T), polyhexamethylene isophthalamide (polyamide 6I), polyhexamethylene terephthal / isophthalamide (polyamide 6T / 6I), polybis (4-aminocyclohexyl) methadodecamide (polyamide PACM12). , Polybis (3-methyl-4-aminocyclohexyl) methandodecamide (polyamide dimethyl PACM12), polymethaxylylene adipamide (polyamide MXD6), polynonamethylene terephthalamide (polyamide 9T), polydecamethylene terephthalamide (polyamide 10T) ), Polyundecamethylene terephthalamide (polyamide 11T), polyundecamethylene hexahydroterephthalamide (polyamide 11T (H)), and copolymers and mixtures thereof. Of these, polyamide 6, polyamide 66, polyamide 11, polyamide 12, and copolymers and mixtures thereof are preferable.

Examples of the cellulose fiber used in the present invention include those derived from wood, rice, cotton, hemp, kenaf and the like, those derived from organisms such as bacterial cellulose, baronia cellulose and squirrel cellulose, regenerated cellulose and cellulose derivatives.

In order to obtain a foam molded product having a uniform size and a large number of fine foam cells, it is preferable to uniformly disperse the cellulose fibers in the resin composition without aggregating them. For this purpose, the dispersibility of the cellulose fiber with respect to the polyamide resin and the affinity between the polyamide resin and the cellulose fiber are important. In addition, it is important to increase the surface area of the cellulose fibers in order to exert the properties of the cellulose fibers as much as possible. Therefore, it is preferable to use cellulose fibers as fine as possible.

The cellulose fibers contained in the polyamide resin composition of the present invention need to have an average fiber diameter of 10 μm or less, preferably 1 μm or less, more preferably 300 nm or less, and at 40 to 100 nm. It is more preferable to have. When the average fiber diameter of the cellulose fibers exceeds 10 μm, the surface area of the cellulose fibers cannot be increased, and it becomes difficult to improve the dispersibility and affinity for the polyamide resin. As a result, in the foamed molded product obtained from the polyamide resin composition using the cellulose fibers, the size of the foamed cells may not be uniform or the foamed cells may become large. In addition, agglomerates of cellulose fibers can be visually confirmed, and the surface appearance and impact resistance are inferior.

In order to make the average fiber diameter of the cellulose fibers in the polyamide resin composition 10 μm or less, it is preferable to use cellulose fibers having an average fiber diameter of 10 μm or less.

Examples of cellulose fibers having an average fiber diameter of 10 μm or less include those microfibrillated by tearing the cellulose fibers, aggregates of cellulose fibers produced as waste threads, bacterial cellulose produced by bacteria, and cellulose fibers. Examples thereof include cellulose fibers that have been oxidized and then refined.

Microfibrillated cellulose fibers can be obtained by tearing the cellulose fibers using various crushing devices such as a ball mill, a stone mill crusher, a high-pressure homogenizer, and a mixer. Examples of commercially available products include "Serish" manufactured by Daicel FineChem.

The aggregate of cellulose fibers produced as waste yarn can be obtained by waste yarn at the time of spinning, weaving, manufacturing a non-woven fabric, and processing of textile products. Since the aggregate of these cellulose fibers is a waste thread after the cellulose fibers have undergone the above steps, the cellulose fibers are made finer.

Examples of the bacterial cellulose produced by bacteria include those produced by acetic acid bacteria of the Acetobacter group as producing bacteria. Plant cellulose is formed by converging the molecular chains of cellulose and is formed by bundling very thin microfibrils, whereas cellulose produced by acetic acid bacteria originally has a width of 20 to 50 nm. It is ribbon-shaped and forms an extremely fine network compared to plant cellulose.

Examples of the cellulose fibers that have been refined after oxidizing the cellulose fibers include those obtained by oxidizing the cellulose fibers in the presence of an N-oxyl compound, washing them with water, and physically defibrating them. Examples of the N-oxyl compound include 2,2,6,6-Tetrapiperidine-1-oxyl radical.

The cellulose fibers in the polyamide resin composition in the present invention preferably have an aspect ratio (average fiber length / average fiber diameter), which is a ratio of the average fiber diameter to the average fiber length, of 10 or more, and preferably 50 or more. Is more preferable, and 100 or more is further preferable. When the aspect ratio is 10 or more, the mechanical properties of the obtained foamed molded product can be easily improved.

The content of the cellulose fibers in the polyamide resin composition needs to be 0.1 to 10.0 parts by mass with respect to 100 parts by mass of the polyamide resin, and is 0.5 to 10.0 parts by mass. It is preferably 0.5 to 5.0 parts by mass, and more preferably 0.5 to 5.0 parts by mass. When the content of the cellulose fiber is less than 0.1 parts by mass, it becomes difficult to foam in the foam molding, and it is not possible to obtain a foam molded product having a uniform size and a large amount of fine foam cells, which is not preferable. On the other hand, when the content of the cellulose fibers exceeds 10.0 parts by mass, it becomes difficult to contain the cellulose fibers in the polyamide resin composition, or the size of the foam cells in the obtained foamed molded product is non-uniform. It is not preferable because it becomes.

Above all, by obtaining the polyamide resin composition of the present invention by a production method as described later, even if the content of the cellulose fibers is small, the polyamide resin composition is uniformly dispersed in the polyamide resin. Therefore, in foam molding, it is possible to obtain a foam molded product that is sufficiently foamed, has a uniform size, and has a large amount of fine foam cells.

Cellulose fibers have a very high affinity for water, and the smaller the average fiber diameter, the better the dispersed state in water can be maintained. Further, when water is lost, the cellulose fibers are strongly aggregated by hydrogen bonds, and once aggregated, it becomes difficult to obtain the same dispersed state as before the aggregation. In particular, this tendency becomes more remarkable as the average fiber diameter of the cellulose fibers becomes smaller. Therefore, it is preferable that the cellulose fiber is composited with the polyamide resin in a state of containing water. In the present invention, a polyamide resin composition containing cellulose fibers is obtained by advancing the polymerization reaction of the monomers constituting the polyamide resin in the presence of water-containing cellulose fibers during the polymerization of the polyamide resin. It is preferable to adopt the method. By such a manufacturing method, it becomes possible to uniformly disperse the cellulose fibers in the polyamide resin without agglomerating them.

In the present invention, it is necessary to use a polyfunctional compound for the purpose of improving the stretch viscosity of the obtained polyamide resin composition. Examples of the polyfunctional compound include a polyfunctional epoxy compound, a polyfunctional isocyanate compound, a polyfunctional carbodiimide compound, and a polyfunctional carboxylic acid anhydride. Of these, polyfunctional epoxy compounds and polyfunctional carbodiimide compounds are preferable from the viewpoints of reactivity, reaction temperature, versatility, and cost. The polyfunctional compound may be used alone or in combination. The polyfunctional compound preferably has 2 to 100 functional groups per molecular chain.

Examples of the polyfunctional epoxy compound include a low molecular weight polyfunctional epoxy compound and a high molecular weight polyfunctional epoxy compound. Examples of the low-molecular-weight polyfunctional epoxy compound include polyglycidyl ether compounds, and examples of commercially available products include "SR-TMP" manufactured by Sakamoto Yakuhin Kogyo Co., Ltd. and "Denacol EX-521" manufactured by Nagase ChemteX Corporation. Can be mentioned. Examples of the polyfunctional epoxy compound of the polymer include those containing polyethylene resin, acrylic resin, acrylic / styrene copolymer, silicone / acrylic copolymer, and polyethylene glycol resin as main components. Examples of commercially available products containing polyethylene resin as a main component include "Bond Fast E" manufactured by Sumitomo Chemical Co., Ltd. Examples of commercially available products containing an acrylic resin as a main component include "Rezeda GP-301" and "ARUFONUG-4000" manufactured by Toagosei Co., Ltd. and "Metabrene KP-7653" manufactured by Mitsubishi Rayon Co., Ltd. Examples of commercially available products containing an acrylic / styrene copolymer as a main component include "Joncryl-ADR-4368" manufactured by BASF and "ARUFON UG-4040" manufactured by Toagosei. Examples of commercially available products containing a silicone / acrylic copolymer as a main component include "Metabrene S-2200" manufactured by Mitsubishi Rayon Corporation. Examples of commercially available products containing polyethylene glycol resin as a main component include Epiol "E-1000" manufactured by NOF CORPORATION.

Examples of the polyfunctional isocyanate compound include monomeric MDI (MDI: methylenebis (4,1-phenylene) diisocyanate), polypeptide MDI, and aromatic polyisocyanate. Examples of commercially available products of monomeric MDI include "Luplanate MS" manufactured by BASF. Examples of commercially available products of Polymeric MDI include "Millionate MR-200" manufactured by Nippon Polyurethane Industry Co., Ltd. and "Luplanate M20S" manufactured by BASF. Examples of commercially available aromatic polyisocyanates include "Millionate MT" manufactured by Nippon Polyurethane Industry Co., Ltd.

Examples of the polyfunctional carbodiimide compound include aromatic polycarbodiimide and aliphatic (alicyclic) polycarbodiimide. Examples of commercially available aromatic polycarbodiimides include "STAVACSOL P" and "STAVACSOL P-400" manufactured by Rheinchemy. Examples of commercially available aliphatic (alicyclic) polycarbodiimides include "Carbodilite LA-1" manufactured by Nisshinbo Holdings.

Examples of the polyfunctional oxazoline compound include aromatic polyoxazolines such as 1,3-phenylene-bisoxazoline and oxazoline-containing polymers. Examples of commercially available oxazoline-containing polymers include "Epocross" manufactured by Nippon Shokubai Co., Ltd.

Examples of the polyfunctional carboxylic acid anhydride include pyromellitic anhydride, benzophenone tetracarboxylic acid dianhydride, cyclopentanetetracarboxylic acid dianhydride, and diphenylsulfone tetracarboxylic acid dianhydride.

The molecular weight of the polyfunctional compound is preferably 2000 to 20000, more preferably 2000 to 100,000, and even more preferably 5000 to 50000. If the molecular weight is less than 2000, problems such as decomposition, volatilization, and non-uniform dispersion occur when reacting with the aromatic polyamide by melt-kneading, which may reduce operability and manufacturability. On the other hand, when the molecular weight exceeds 200,000, the effect of increasing the elongation viscosity may be small or the dispersion may not be uniform. As the molecular weight of the polyfunctional compound, the weight average molecular weight measured by gel permeation chromatography (GPC) can be used. The eluate used in the measurement is selected in consideration of the solubility of the sample in the eluate, and examples thereof include chloroform, hexafluoroisopropanol, and tetrahydrofuran.

The content of the polyfunctional compound in the polyamide resin composition needs to be 0.1 to 5.0 parts by mass with respect to 100 parts by mass of the polyamide resin, and is 0.2 to 3.0 parts by mass. It is preferably 0.3 to 1.0 parts by mass, and more preferably 0.3 to 1.0 parts by mass. When the content of the polyfunctional compound is less than 0.1 parts by mass, the compounding effect is small, which is not preferable. On the other hand, when the content of the polyfunctional compound exceeds 5.0% by mass, the fluidity at the time of melting is poor and the handling becomes difficult, which is not preferable.

In the present invention, a bubble adjusting agent may be used for the purpose of producing a foam molded product having finer bubbles. Examples of the bubble adjusting agent include titanium oxide, talc, kaolin, clay, calcium silicate, silica, sodium citrate, calcium carbonate, diatomaceous soil, calcined pearlite, zeolite, bentonite, glass, limestone, calcium sulfate, aluminum oxide, and titanium oxide. , Magnesium carbonate, sodium carbonate, ferric carbonate, polytetrafluoroethylene powder, calcium. Such a bubble adjusting agent preferably has an average particle size of 100 μm or less from the viewpoint of reducing the generated bubbles. The bubble adjusting agent may be added in advance to the polyamide resin composition or may be added at the time of foaming.

When the bubble adjusting agent is used, the content thereof is preferably 0.01 to 5 parts by mass, more preferably 0.1 to 3 parts by mass with respect to 100 parts by mass of the polyamide resin. If the content of the bubble adjusting agent is less than 0.01% by mass, the bubbles of the foamed molded product may become coarse and the appearance may be impaired. On the other hand, when the content of the bubble adjusting agent exceeds 5% by mass, foam breakage frequently occurs during extrusion foaming, and the closed cell ratio may decrease or the appearance may be impaired.

The polyamide resin composition of the present invention may contain other resins in addition to the polyamide resin and the polyfunctional compound as long as the effects of the present invention are not impaired.

Other resins include, for example, polyester resin, polyolefin resin, polystyrene resin, polyacrylic acid, polycarbonate resin, polyarylate resin, fluororesin, polyacetal resin, polyvinylidene fluoride, polysulfone, polyphenylene sulfide, polyethersulfone, phenoxy resin, and the like. Examples thereof include elastomers such as modified polyphenylene ethers, polyether ketones, and polybutadienes. Other resins may be used alone or in combination of two or more.

When another resin is used, the content thereof is preferably 10% by mass or less, preferably 5% by mass, based on the entire polyamide resin composition from the viewpoint of maintaining the uniformity and heat resistance of the polyamide resin composition. The following is more preferable.

The polyamide resin composition of the present invention further includes a heat stabilizer, an antioxidant, a pigment, a weather resistant agent, a flame retardant, a plasticizer, a dispersant, a lubricant, a mold release agent, and a charge, as long as the effects of the present invention are not impaired. Additives such as inhibitors, crosslinkers, chain extenders, end sealants, fillers and reinforcements may be added. The additive may be added at the time of polymerization, melt kneading or extrusion foaming.

Examples of heat stabilizers and antioxidants include phosphite organic compounds, hindered phenol compounds, benzotriazole compounds, triazine compounds, hindered amine compounds, sulfur compounds, copper compounds, alkali metal halides, and phosphorus. Examples include compounds or mixtures thereof.

Examples of the terminal sequestering agent include carbodiimide compounds other than polyfunctional compounds, oxazoline compounds, and epoxy compounds.

Dispersants include, for example, industrial oils such as liquid paraffin, mineral oil, cleosort oil, lubricating oil and silicone oil, vegetable oils such as corn oil, soybean oil, rapeseed oil, palm oil, flaxseed oil and jojoba oil, and ionic. And nonionic surfactants.

Examples of the filler include an inorganic filler and an organic filler. Examples of the inorganic filler include talc, layered silicate, calcium carbonate, zinc carbonate, wallastnite, silica, alumina, magnesium oxide, calcium silicate, sodium aluminate, calcium aluminate, sodium aluminosilicate, magnesium silicate, and the like. Examples thereof include glass balloon, carbon black, zinc oxide, antimony trioxide, zeolite, hydrotalcite, metal fiber, metal whisker, ceramic whisker, potassium titanate, boron nitride, graphite, glass fiber and carbon fiber. Examples of the organic filler include naturally occurring polymers such as starch, cellulose fine particles, wood flour, bean curd refuse, fir shells, bran, and kenaf, and modified products thereof.

The method for producing the polyamide resin composition of the present invention is not particularly limited, but for example, a polyamide resin containing cellulose fibers having an average fiber diameter of 10 μm or less in advance (hereinafter, may be abbreviated as “cellulose-containing polyamide resin”). Is mentioned, and a method of melt-kneading the cellulose-containing polyamide resin and the polyfunctional compound can be mentioned.

The cellulose-containing polyamide resin can be obtained by mixing an aqueous dispersion of cellulose fibers and a monomer constituting the polyamide resin and advancing the polymerization reaction.

The aqueous dispersion of cellulose fibers can be obtained by stirring purified water and cellulose fibers with a mixer or the like. The content of the cellulose fibers in the aqueous dispersion is preferably 0.01 to 50% by mass.

The polymerization reaction is preferably carried out at 150 to 270 ° C. At the time of polymerization, a catalyst such as phosphoric acid or phosphorous acid may be added if necessary. Then, after the completion of the polymerization reaction, it is preferable that the obtained polyamide resin composition is discharged and then cut into pellets.

When bacterial cellulose is used as the cellulose fiber, the aqueous dispersion of the cellulose fiber may be obtained by immersing the bacterial cellulose in purified water and substituting the solvent. When a solvent-substituted bacterial cellulose is used, it is preferable that the solvent is replaced, the concentration is adjusted to a predetermined concentration, and then the mixture is mixed with a monomer constituting the polyamide resin to allow the polymerization reaction to proceed in the same manner as described above.

In the present invention, by using cellulose fibers having an average fiber diameter of 10 μm or less and subjecting the cellulose fibers to the polymerization reaction as an aqueous dispersion, the cellulose fibers can be subjected to the polymerization reaction in a state of good dispersibility. Further, the cellulose fibers subjected to the polymerization reaction have improved dispersibility by interacting with the monomers and water during the polymerization reaction and by stirring under the above-mentioned temperature conditions, so that the fibers aggregate with each other. It is possible to obtain a polyamide resin in which cellulose fibers having a small average fiber diameter are well dispersed. According to the above method, since the dispersibility of the cellulose fibers is improved, the cellulose fibers contained in the mixture after the completion of the polymerization reaction are larger than the average fiber diameter of the cellulose fibers added before the polymerization reaction. The average fiber diameter and fiber length may be small.

Further, in the above method, the step of drying the cellulose fibers is not required, and the production can be performed without going through the step of causing the fine cellulose fibers to scatter, so that the cellulose fiber-containing polyamide resin can be obtained with good operability. Become. Further, since it is not necessary to replace water with an organic solvent for the purpose of uniformly dispersing the monomer and cellulose, it is possible to improve the handling and suppress the discharge of chemical substances during the manufacturing process.

The relative viscosity of the cellulose fiber-containing polyamide resin is not particularly limited, but is preferably 1.5 to 7.0, and more preferably 1.7 to 6.0. When the relative viscosity is less than 1.5, it is difficult to form a uniform foam cell, the foam moldability is lowered, and the mechanical properties may also be lowered. On the other hand, when the relative viscosity exceeds 7.0, the fluidity of the cellulose fiber-containing polyamide resin is lowered, so that the foam moldability may be lowered. The method for measuring the relative viscosity will be described later, but it was carried out under the conditions of using 96% sulfuric acid as a solvent, a temperature of 25 ° C., and a concentration of 1 g / 100 ml.

Originally, the polyamide resin has a low elongation viscosity and does not have foaming suitability. On the other hand, in the present invention, since the polyamide resin, the cellulose fiber and the polyfunctional compound are reacted to increase the elongation viscosity, a polyamide resin composition having foaming suitability can be obtained.

The extensional viscosity of the cellulose fiber-containing polyamide resin ^{is preferably 8.00 × 10 3 to} 5.00 × 10 ⁶ Pa · s, preferably 1.00 × 10 ^{4 to} 3.0 × 10 ⁶ Pa · s. More preferably, it is 1.00 × 10 ^{4 to} 9.50 × 10 ⁴ Pa · s. When the extensional viscosity is in the range of 8.00 × 10 ^{3 to} 5.00 × 10 ⁶ Pa · s, the viscosity is suitable for foaming, and the size of the foamed cell is uniform and has an appropriate size. Since a large number of foam cells are formed, the surface appearance and impact resistance are excellent.

^{Among them, the cellulose fiber-containing polyamide resin having an elongation viscosity of 1.00 × 10 4 to} 9.50 × 10 ⁴ Pa · s, which is a preferable range, has the above-mentioned average fiber diameter of the cellulose fibers in the polyamide resin composition. It can be prepared by setting the temperature to 40 to 100 nm, which is the most preferable range, and setting the content of the cellulose fiber to 0.5 to 5 parts by mass, which is the most preferable range described above. Even if the average fiber diameter of the cellulose fibers in the cellulose fiber-containing polyamide resin exceeds the most preferable range of 40 to 100 nm, the elongation viscosity of the cellulose fiber-containing polyamide resin remains 1.00 × 10 ^{4 to} 3. It may be in the range of 0 × 10 ⁶ Pa · s, but when the average fiber diameter of the cellulose fibers exceeds 100 nm, the obtained foamed molded product has foamed cells having a large cell diameter, which is slightly inferior in uniformity. Cheap. Therefore, in the present invention, the average fiber diameter of the cellulose fibers of the cellulose fiber-containing polyamide resin is preferably 40 to 100 nm.

The extensional viscosity is generally a measure of the stickiness of the molten resin when foaming the thermoplastic resin, and in the present invention, it indicates the ease of extrusion foam molding. The extensional viscosity is calculated by Cogswell's theoretical formula based on the shear viscosity measured by the following method.

The shear rate can be calculated using the following formula from the melt viscosity measured using two types of dies with different capillary lengths under the condition (melting point of cellulose fiber-containing polyamide resin + 30 ° C.) with a capillary rheometer. .. Hereinafter, the capillary length is L and the capillary diameter is D.

ここで、τｃ：補正せん断応力（Ｐａ）である。

ここで、Ｄ ：キャピラリ直径（ｍｍ）、Ｐｃ：キャピラリ内圧力損失（Ｐａ）である。 The extensional viscosity ηe (Pa · s) is calculated by the following formula.

Here, τc: corrected shear stress (Pa).

Here, D: capillary diameter (mm), Pc: pressure loss in the capillary (Pa).

ここで、γｃ：補正せん断速度（ｓ^−１）、γａ：見掛けのせん断速度（ｓ^−１）、ｎ：べき法則指数である。
ｎは、横軸にｌｏｇ（τｃ）、縦軸にｌｏｇ（γａ）をプロットしたときの傾きとして求めることができる。 The section on the vertical axis obtained from the linear equations of L / D (horizontal axis) and resin pressure (vertical axis) when the resin pressure at the same shear rate is measured with each die is defined as Pc (Bagley correction).

Here, γc: corrected shear rate (s ^-1 ), γa: apparent shear rate (s ^-1 ), n: power law index.
n can be obtained as the slope when log (τc) is plotted on the horizontal axis and log (γa) is plotted on the vertical axis.

The method for melt-kneading the cellulose fiber-containing polyamide resin and the polyfunctional compound is not particularly limited as long as it can be uniformly melt-kneaded, and examples thereof include a melt-kneading method using an ordinary extruder.

The foam molded product of the present invention can be obtained by extrusion foam molding the polyamide resin composition of the present invention. As the foaming agent, a thermal decomposition type foaming agent, a physical foaming agent, or the like can be used.

The pyrolytic foaming agent is a foaming agent that foams a resin by generating gas when heated to a temperature higher than the decomposition temperature. Examples of the heat-decomposable foaming agent include azo compounds such as azodicarbonamide and barium azodicarboxylate, nitroso compounds such as N, N'-dinitrosopentamethylenetetramine, and 4,4'-oxybis (benzenesulfonylhydrazide). , Hydrazine compounds such as hydrazicarbonamide, tetrazole compounds, and inorganic foaming agents such as sodium hydrogencarbonate. Of these, a tetrazole compound having a high decomposition temperature is preferable. The pyrolytic foaming agent may be used alone or in combination of two or more. The method of blending the pyrolyzable foaming agent into the polyamide resin composition is not particularly limited, and examples thereof include a method of supplying the pyrolyzable foaming agent together with the polyamide resin composition to the extruder.

The physical foaming agent is a foaming agent that foams a resin by a gas expanded by a temperature change or a pressure change without a chemical reaction. Examples of the physical foaming agent include inorganic compounds such as nitrogen, carbon dioxide and water, various hydrocarbons such as methane, ethane, propane, butane and pentane, freon compounds, ethers such as dimethyl ether and methyl ethyl ether, ethanol and the like. Examples thereof include organic solvents typified by various alcohols such as methanol. The method of blending the physical foaming agent into the polyamide resin composition is not particularly limited, and examples thereof include a method of supplying the polyamide resin composition to an extruder and injecting the physical foaming agent from the middle of the extruder.

The blending amount of the foaming agent is preferably 0.05 to 10% by mass, more preferably 0.1 to 6% by mass, based on the polyamide resin composition. If the blending amount of the foaming agent is less than 0.05% by mass, a foamed molded product that is sufficiently foamed (high foaming ratio) may not be obtained. On the other hand, when the blending amount of the foaming agent exceeds 10% by mass, foam breakage may occur, or air bubbles may coalesce inside the foamed molded product, and the appearance of the foamed molded product may be impaired.

Since the polyamide resin composition of the present invention has excellent foaming properties, the foaming ratio [(apparent density of foamed molded product) / (apparent density of polyamide resin composition)] described later can be doubled or more by foam molding. Can be.

The dimensional stability of the foamed molded product of the present invention during water absorption is preferably less than ± 3% in both the length change rate and the width change rate in the evaluation of dimensional stability described later. Since a polyamide resin is generally a resin that easily absorbs water, a molded product using a polyamide resin is generally required to have a small rate of change during long-term use. If both rates of change are less than ± 3%, it can be said that there is no practical problem even when used as a foam molded product. The rate of change of both is less than ± 3%, which can be achieved by using a polyamide resin containing cellulose having an average fiber diameter of 10 μm or less and a specific amount of a polyfunctional compound in combination.

The method for producing the foamed molded product is not particularly limited, and for example, the polyamide resin composition is extruded and foamed from a slit-shaped nozzle to form a sheet (foamed sheet) using an extruder, or extruded and foamed from a round nozzle. There is a method of forming a strand shape (foamed strand). By cutting the foamed sheet or foamed strand, the shape of the foamed molded product can be made into particles. Further, the obtained extruded foamed molded product can be thermoformed as it is, or can be cut into foamed particles and then molded in a mold.

The extruder used for producing the foam molded product of the present invention is not particularly limited, and examples thereof include a single-screw extruder, a twin-screw extruder, and a tandem type extruder in which a plurality of extruders are connected.

Since the polyamide resin composition of the present invention is excellent in foaming performance, the foamed molded product thereof is a packaging material, a packaging material, a cushioning material, a heat insulating material, a heat insulating material, a cold insulating material, a sound deadening material, a sound absorbing material, a soundproofing material, and the like. It can be suitably used for vibration damping materials, building materials, cushioning materials, materials, containers and the like. Specifically, sofas, bed mats, chairs, bedding, mattresses, light covers, stuffed animals, slippers, cushions, helmets, carpets, pillows, shoes, pouches, mats, crash pads, sponges, stationery, toys, DIY supplies, panels. , Tatami core material, mannequin, automobile interior parts / cushions, car seats, deadening, door trims, sun visors, automobile vibration damping materials / sound absorbing materials, sports mats, fitness equipment, sports protectors, beat boards, ground fences, leisure Sheets, medical mattresses, medical supplies, nursing care products, rehabilitation products, building insulation materials, building joint materials, face door materials, building curing materials, reflective materials, industrial trays, tubes, pipe covers, air conditioner insulation pipes, gasket cores Materials, concrete molds, civil engineering joints, anti-scratch panels, protective materials, lightweight soil, fillings, artificial soil, packaging materials / packaging materials, packaging materials, wrapping, packaging materials / packaging materials for fresh products / vegetables / fruits, etc., electronic Packaging materials / buffer packaging materials for equipment, heat / cold storage boxes for fresh products / vegetables / fruits, food containers such as cup ramen / lunch boxes, edible trays, beverage containers, agricultural materials, foam models, vibrating plates for speakers And so on.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.

A. Evaluation method (1) Average fiber diameter of cellulose fiber (1-1) Average fiber diameter of cellulose fiber before polymerization reaction If necessary, freeze-dried cellulose fiber is subjected to an electric field radiation scanning electron microscope (S. manufactured by Hitachi, Ltd.). -Observed using (4000). The length of the cellulose fiber (single fiber) in the direction perpendicular to the longitudinal direction was measured from an electron microscope (SEM) image. At this time, the maximum length in the vertical direction was defined as the fiber diameter. In the same manner, the fiber diameters of 10 cellulose fibers (single fibers) were measured, and the average value of the 10 fibers was calculated and used as the average fiber diameter.

(1-2) Average Fiber Diameter of Cellulose Fibers in Resin Composition A section having a thickness of 100 nm was collected from a foamed molded product using a frozen ultramicrotome, and section dyeing was performed with _{OsO 4 (osmium tetroxide).} Observation was performed using a transmission electron microscope (JEM-1230 manufactured by JEOL Ltd.). The length of the cellulose fiber (single fiber) in the direction perpendicular to the longitudinal direction was measured from the electron microscope image. At this time, the maximum length in the vertical direction was defined as the fiber diameter. In the same manner, the fiber diameters of 10 cellulose fibers (single fibers) were measured, and the average value of the 10 fibers was calculated and used as the average fiber diameter.
For cellulose fibers with a large fiber diameter, a section of 10 μm was cut out with a microtome, or the foamed molded product was observed as it was with a stereomicroscope (OLYMPUS SZ-40). The fiber diameter was measured from the obtained image in the same manner as above, and the average fiber diameter was obtained.

(2) Content of Cellulose Fiber in Resin Composition The content was measured under the following conditions using a TG / DTA 7200 device manufactured by SII Nanotechnology.
Weigh sufficiently dried cellulose and resin in a special pan so that they have known concentrations, and create a calibration curve with the weight reduction from 290 ° C to 320 ° C as the amount of cellulose in the resin. The content of cellulose fibers in the obtained foamed molded product was calculated.
At this time, the foamed molded product was freeze-crushed and used, and a sample amount of 10 mg was weighed with a precision balance to measure the temperature rise in a nitrogen atmosphere. The temperature raising conditions are as follows: the temperature is raised from 30 ° C. to 285 ° C. at 5 ° C./min, the temperature is raised from 285 ° C. to 320 ° C. at 0.63 ° C./min, and the temperature is raised again from 320 ° C. to 350 ° C. at 5 ° C./min. Finally, the temperature was raised from 350 ° C. to 550 ° C. at 10 ° C./min.

(3) Relative viscosity of polyamide resin or cellulose fiber-containing polyamide resin Cellulose fiber-containing polyamide resin (treated with hot water at 95 ° C, refined and dried) is used at 96% sulfuric acid at a temperature of 25 ° C. , The relative viscosity was determined under the condition of concentration 1 g / 100 ml.

(4) Extensional viscosity of cellulose fiber-containing polyamide resin The shear viscosity ηc (Pa · s) of the cellulose fiber-containing polyamide resin was measured under a predetermined temperature condition using a capillary rheometer (CFT-500D manufactured by Shimadzu Corporation), and the above-mentioned theory was obtained. The extensional viscosity ηe (Pa · s) was determined according to the above. As the die 1, two types of dies having a capillary length of 15 mm and a capillary diameter of 1 mmφ and as a die 2 having a capillary length of 0.25 mm and a capillary diameter of 1 mmφ were used.

(5) Foaming Performance of Polyamide Resin Composition The masses of the polyamide resin composition (before foaming) and the foamed molded product are measured, and the apparent volumes thereof are measured by a wet electron specific gravity meter (manufactured by Alpha Mirage Co., Ltd., trade name "EW". -300SG ") was used for measurement. For the polyamide resin composition and the foamed molded product, the apparent density was calculated from the ratio of the apparent volume to the mass. Then, the foaming ratio was calculated from the following formula.
Foaming magnification of foam molded product = (apparent density of foamed molded product) / (apparent density of polyamide resin composition)
The foaming performance was evaluated according to the following criteria.
◯: The foaming ratio is 2 times or more.
X: The foaming ratio is less than 2 times.

(6) Dimensional stability of the foamed molded product during water absorption The obtained foamed molded product was absorbed by water immersion at 25 ° C., and 10% by mass of water was absorbed with respect to the total mass of the foamed molded product. The length and width of the foamed molded product before and after the water absorption treatment were measured, and the dimensional change rate in the length and width was calculated from the following formula.
Dimensional change rate (%) = [(YX) / X] x 100
X: Length or width of the foamed molded product before the water absorption treatment Y: Length or width of the foamed molded product after the water absorption treatment The evaluation was made according to the following two-step criteria based on the value of the dimensional change rate.
◯: Both the length change rate and the width change rate are less than ± 3% ×: At least one of the length change rate and the width change rate is ± 3% or more.

B. Raw materials (1) Preparation of cellulose fiber aqueous dispersion (1-1) Cellulose fiber aqueous dispersion 1
Purified water is added to Serish KY100G (manufactured by Daicel FineChem: containing 10% by mass of cellulose fibers having an average fiber diameter of 125 nm) and stirred with a mixer. Cellulose fiber water having a cellulose fiber content of 3% by mass. Dispersion 1 was prepared.

(1-2) Cellulose fiber aqueous dispersion 2
Serish KY100S (manufactured by Daicel FineChem) was used as it was.

(1-3) Cellulose fiber aqueous dispersion 3
Serish KY100G (manufactured by Daicel FineChem: containing 10% by mass of cellulose fibers having an average fiber diameter of 125 nm) was used as it was.

(1-4) Cellulose Fiber Short fibers of cotton (average fiber diameter 16 μm) were used.

(2) Polyamide resin (2-1) Cellulose fiber-containing polyamide resin (A-1)
70 parts by mass of the cellulose fiber aqueous dispersion 1 and 100 parts by mass of ε-caprolactam were further stirred and mixed with a mixer until a uniform dispersion was obtained. Subsequently, the mixed dispersion was heated to 240 ° C. with stirring, and the pressure was increased from 0 MPa to 0.7 MPa while gradually releasing water vapor. Then, the pressure was released to atmospheric pressure, and the polymerization reaction was carried out at 240 ° C. for 1 hour. After completion of the polymerization, the polymer was discharged, cut into pellets, treated with hot water at 95 ° C., refined and dried to obtain a cellulose-containing polyamide resin (A-1).
The relative viscosity of the obtained cellulose-containing polyamide resin was 2.45.

(2-2) Cellulose fiber-containing polyamide resin (A-2)
70 parts by mass of the cellulose fiber aqueous dispersion 2 and 100 parts by mass of ε-caprolactam were further stirred and mixed with a mixer until a uniform dispersion was obtained. Subsequently, the mixed dispersion was heated to 240 ° C. with stirring, and the pressure was increased from 0 MPa to 0.7 MPa while gradually releasing water vapor. Then, the pressure was released to atmospheric pressure, and the polymerization reaction was carried out at 240 ° C. for 1 hour. After completion of the polymerization, the polymer was discharged, cut into pellets, treated with hot water at 95 ° C., refined and dried to obtain a cellulose-containing polyamide resin (A-2).

(2-3) Cellulose fiber-containing polyamide resin (A-3)
A cellulose-containing polyamide resin (A-3) was obtained in the same manner as in Example 1 except that 100 parts by mass of the cellulose fiber aqueous dispersion 2 and 100 parts by mass of ε-caprolactam were used.
The relative viscosity of the obtained cellulose-containing polyamide resin was 2.47.

(2-3) Cellulose fiber-containing polyamide resin (A-4)
A cellulose-containing polyamide resin (A-4) was obtained in the same manner as in Example 1 except that 2 parts by mass of cellulose fibers and 100 parts by mass of ε-caprolactam were used.
The relative viscosity of the obtained cellulose-containing polyamide resin was 2.44.

(2-4) Polyamide 6 resin (A-5)
-Unitika "A1030BRL", melting point: 225 ° C, relative viscosity: 2.5

(3) Polyfunctional compound (3-1) Polyfunctional epoxy compound (B-1)
-Trimethylolpropane polyglycidyl ether, "SR-TMP" manufactured by Sakamoto Yakuhin Kogyo Co., Ltd., weight average molecular weight: 254

(3-2) Polyfunctional carbodiimide compound (B-2)
-Nisshinbo's "Carbodilite LA-1", weight average molecular weight: 5000

(4) Foaming agent / carbon dioxide

(5) Bubble conditioner, fine talc "MW-HST" manufactured by Hayashi Kasei Co., Ltd., average particle size: 2.5 μm

Example 1
102.1 parts by mass of cellulose fiber-containing polyamide resin (A-1) and 0.6 parts by mass of polyfunctional compound (B-1) are dry-blended and a twin-screw extrusion kneader (manufactured by Ikegai Corp., "PCM-30"). ”) Was supplied from the base and melt-kneaded. After taking it into a strand shape from the die, it was passed through a water tank to be cooled and solidified, and it was cut with a pelletizer to obtain a polyamide resin composition. A screw having a diameter of 29 mm and an L / D of 30 was used, and a nozzle having 4 mm × 3 holes was used. The upstream temperature of the kneader was set to 260 ° C, the middle and downstream temperatures were set to 320 ° C, and the die outlet temperature was set to 320 ° C. The discharge rate was 3 kg / h.
Subsequently, 102.7 parts by mass of the obtained polyamide resin composition and 1.0 part by mass of fine powder talc are dry-blended and supplied from the base of a twin-screw extruder (manufactured by Ikekai Co., Ltd., "PCM-30"). Then, carbon dioxide was injected from the middle of the extruder using a liquefied carbon dioxide gas injection device (manufactured by Showa Carbonate Co., Ltd.) and extruded to produce a sheet-shaped foam molded product. A screw having a diameter of 29 mm and an L / D of 30 was used, and a die having a ^{slit of 0.8 mm t} × 33 mm was used. The upstream temperature of the kneader was set to 230 ° C, the middle and downstream temperatures were set to 210 ° C, and the die outlet temperature was set to 220 ° C. The discharge rate was 5 kg / h. The foaming ratio of the obtained foamed molded product was 7 times.

Examples 3 to 7, Reference Example 1, Comparative Examples 1 to 5
A polyamide resin composition and a foamed molded product thereof were obtained in the same manner as in Example 1 except that the composition to be blended was changed so that the resin composition was as shown in Table 1.

Table 1 shows the characteristic values of the polyamide resin compositions obtained in Examples 1 , 3 to 7, Reference Example 1, and Comparative Examples 1 to 5 and the foamed molded product thereof.

The polyamide resin compositions obtained in Examples 1 , 3 to 7 all had an elongation viscosity of 1.0 × 10 ⁵ Pa. It was s or more and was excellent in foaming performance. In addition, the foam molded product obtained from it was excellent in dimensional stability during water absorption.

Since the polyamide resin composition of Comparative Example 1 did not contain a polyfunctional compound, the foaming performance was poor.
Since the polyamide resin composition of Comparative Example 2 contained a large amount of the polyfunctional compound, the foaming performance was poor and the dimensional stability at the time of water absorption was poor.
Since the polyamide resin composition of Comparative Example 3 did not contain cellulose fibers having an average fiber diameter of 10 μm or less, the foaming performance was poor and the dimensional stability during water absorption was poor.
The polyamide resin composition of Comparative Example 4 had a poor foaming performance because it contained a large amount of cellulose fibers having an average fiber diameter of 10 μm or less.
Since the polyamide resin composition of Comparative Example 5 used cellulose fibers having an average fiber diameter of more than 10 μm, the foaming performance was poor and the dimensional stability during water absorption was poor.

Claims (2)

Polyamide resin composition containing 100 parts by mass of polyamide resin, 0.1 to 10.0 parts by mass of cellulose fibers having an average fiber diameter of 10 μm or less, and 0.1 to 5.0 parts by mass of trimethylolpropane polyglycidyl ether. .. Foamed molded article comprising the polyamide resin composition according to claim 1 Symbol placement.